//   OData .NET Libraries
//   Copyright (c) Microsoft Corporation. All rights reserved.  
//   Licensed under the Apache License, Version 2.0 (the "License");
//   you may not use this file except in compliance with the License.
//   You may obtain a copy of the License at

//       http://www.apache.org/licenses/LICENSE-2.0

//   Unless required by applicable law or agreed to in writing, software
//   distributed under the License is distributed on an "AS IS" BASIS,
//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//   See the License for the specific language governing permissions and
//   limitations under the License.

namespace Microsoft.OData.Client
{
    using System;
    using System.Diagnostics;
    using System.Linq.Expressions;

    /// <summary>
    /// An resource specific expression representing a query option.
    /// </summary>
    internal abstract class QueryOptionExpression : Expression
    {
        /// <summary>The CLR type this node will evaluate into.</summary>
        private Type type;

        /// <summary>
        /// Creates a QueryOptionExpression expression
        /// </summary>
        /// <param name="type">the return type of the expression</param>
        internal QueryOptionExpression(Type type)
        {
            Debug.Assert(type != null, "type != null");
            this.type = type;
        }

        /// <summary>
        /// The <see cref="Type"/> of the value represented by this <see cref="Expression"/>.
        /// </summary>
        public override Type Type
        {
            get { return this.type; }
        }

        /// <summary>
        /// Composes the <paramref name="previous"/> expression with this one when it's specified multiple times.
        /// </summary>
        /// <param name="previous"><see cref="QueryOptionExpression"/> to compose.</param>
        /// <returns>
        /// The expression that results from composing the <paramref name="previous"/> expression with this one.
        /// </returns>
        internal virtual QueryOptionExpression ComposeMultipleSpecification(QueryOptionExpression previous)
        {
            Debug.Assert(previous != null, "other != null");
            Debug.Assert(previous.GetType() == this.GetType(), "other.GetType == this.GetType() -- otherwise it's not the same specification");
            return this;
        }
    }
}
